CN112485533B - Grounding resistance measuring method based on voltage-current characteristic of down lead - Google Patents
Grounding resistance measuring method based on voltage-current characteristic of down lead Download PDFInfo
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Abstract
The invention discloses a grounding resistance measurement method based on volt-ampere characteristics of a down conductor. The method can conveniently and comprehensively measure the grounding resistance of the grounding electrode and the resistance of the down lead for the multi-down lead grounding system. If a certain grounding down lead is disconnected, the system can realize judgment and does not influence the solution of the equation. If a parameter in the circuit is in the form of impedance, the method is still applicable.
Description
Technical Field
The invention relates to a method for measuring grounding resistance based on voltage-current characteristics of a down lead, which is mainly applied to the field of measurement of grounding resistance of buildings and power transmission lines.
Background
In the aspect of measuring the grounding resistance of the multi-downlead system, the method mainly comprises the following aspects:
1. for a grounding system containing an overhead ground wire or a multi-down conductor, the grounding resistance measured by a loop method is in accordance with the national standard and the industrial specification, and the operation is convenient. During measurement, the down conductor is clamped into the jaw, the clamp meter senses a voltage signal determined by the down conductor through the voltage transformer, and then the current signal is read through the current transformer, and the ratio of the voltage signal to the current signal is the loop resistance. For a grounding system with an overhead ground wire or a multi-down conductor, the loop resistance is regarded as the grounding resistance value. However, if a plurality of downleads are connected to the same grounding electrode, the grounding resistance of the grounding electrode cannot be measured.
2. In the multi-down-lead grounding system, each down lead also has a resistance value, in the actual engineering, the resistance value is counted into the grounding electrode grounding resistance, but the connection relationship exists among the down leads of the multi-down-lead grounding system, and the influence of the down lead grounding resistance on the overall grounding system cannot be reflected in the current operation.
3. For a grounding system with a plurality of downleads connected with the same grounding electrode, the clamp-on meter can only measure the conduction state of each downlead, the measurement value of the clamp-on meter cannot reflect the grounding performance of the grounding system, and the common misoperation phenomenon exists in practical application.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for measuring the grounding resistance based on the volt-ampere characteristic of the downlead, which can conveniently and comprehensively measure the grounding resistance of a grounding electrode and the downlead resistance of a multi-downlead grounding system.
In order to solve the technical problem, the technical scheme adopted by the invention is as follows: the grounding resistance measurement method based on the volt-ampere characteristic of the down conductor comprises the following steps:
s01), constructing a grounding resistance measuring circuit:
the grounding resistance measuring circuit comprises a controller, a sine voltage generating circuit and a current detecting circuit, wherein the sine voltage generating circuit is used for applying measuring voltage to a plurality of downleads of the grounding system, and the current detecting circuit is used for detecting the current generated by the measuring voltage on the downlead and feeding back the current to the controller;
s02), column current-voltage characteristic equation:
firstly, constructing an equivalent circuit of a grounding system, setting the grounding system to have N downleads, regarding the N downleads as N parallel branches, grounding the N downleads through a grounding body, and setting the equivalent resistance of the N downleads as R1～RNThe equivalent resistance of the grounding body is RgDuring measurement, the measuring voltage applied to the N downleads by the sine voltage generating circuit is U1～UNEach down conductor current is I1～INThe voltage across the grounding body is U, thenAccording to the voltammetric characteristics:
Ui＝IiRi+IRg (1)，
both ends are divided by IiThe method comprises the following steps:
finishing to obtain:
for N branches, the above equations are added to obtain
In the formula (4), the first and second groups,
then equation (4) is:
equation (5) is the volt-ampere characteristic equation written in the column;
s03), solving the grounding resistance:
in the grounding system, the equivalent resistance R of the down conductor1～RNEquivalent resistance value of R to grounding bodygFor the quantity to be solved, N +1 unknown quantities are counted, N +1 groups of measurement voltages are applied to the grounding system by utilizing the sine voltage generating circuit, the current generated by each group of measurement voltages in the grounding system is measured by the current measuring circuit, so that N +1 volt-ampere characteristic equations are obtained, and the equivalent resistance R of each downlead is obtained by solving1～RNEquivalent resistance value of R to grounding bodyg。
Furthermore, the grounding resistance measuring circuit also comprises a phase detection circuit, the phase detection circuit carries out phase detection on the measured current data, if the measured current data comprises a resistive part and an inductive part, the current detection circuit feeds the magnitude and the phase of the current back to the controller, and the controller calculates the impedance value of the grounding loop according to the feedback.
Further, in the calculation process, if a certain down conductor fails, the branch is not considered when column voltage-current characteristic equations are written, the number of the equations is reduced in sequence, and the method is still applicable.
Further, the N +1 sets of measurement voltages applied in step S03 are linearly independent, and the N +1 volt-ampere characteristic equations are independent of each other.
Further, U is detected through a clamp meteri/IiAnd the detected value is sent to the controller for calculation.
The invention has the beneficial effects that:
for a multi-down conductor grounding system, comprehensive measurement of grounding electrode grounding resistance and down conductor resistance can be conveniently realized.
Based on a loop method, a voltage transformer is used for inducing voltage to the down conductor, a current transformer is used for collecting the current value on the down conductor, an equation is written in a column mode, the equation is arranged into the voltage-current ratio relation of the down conductor, and the quantity to be solved is obtained.
If a certain grounding down lead is disconnected, the system can realize judgment and does not influence the solution of the equation.
If a parameter in the circuit is in the form of impedance, the method is still applicable.
Drawings
FIG. 1 is a schematic block diagram of a ground resistance measurement circuit;
fig. 2 is an equivalent circuit diagram of the ground resistance.
Detailed Description
The invention is further described with reference to the following figures and specific embodiments.
Example 1
The embodiment discloses a multi-down conductor grounding resistance measuring method based on a node voltage method, which comprises the following steps:
s01), constructing a grounding resistance measuring circuit:
as shown in fig. 1, the ground resistance measuring circuit includes a basic system, a sinusoidal voltage generating circuit, a current detecting circuit, and a phase detecting circuit.
The basic system consists of a power supply module, a serial port module and a main controller MCU. The power supply module is responsible for supplying power to the whole system, can provide various voltage standards and can provide negative voltage when necessary; the serial port module is used for converting the serial port output level of the singlechip into level standards required by peripheral equipment, such as RS232, RS485, CAN and the like, and is conveniently connected with the peripheral equipment; the main controller should build a reset circuit, be equipped with the crystal oscillator and set up the work pilot lamp.
The sinusoidal voltage generating circuit is used for applying a measuring voltage to a plurality of down-leads of the grounding system. The part consists of a signal generation module, a signal amplification module and a power amplification module. The signal generation module can be used for outputting sine waves through programming by a DDC chip, can also be obtained by filtering after being output by a main controller, and can also be directly output by a DA module or a DA chip of the main controller; if the output voltage is smaller, the signal amplification module is required to amplify the output voltage to a larger voltage value; in addition, the circuit needs to drive a voltage transformer, has high power and cannot be directly connected, and therefore the circuit needs to be driven by a power amplification circuit.
The current detection circuit detects the current generated by the measuring voltage on the down conductor and feeds the current back to the controller. The part consists of an IV conversion module, a filtering module, an AC/DC conversion module and an AD conversion module. When the resistance value of the grounding loop is measured, current data is read back through the current transformer, a current signal is converted into a voltage value firstly and then measured, the interference of the read-back signal is large, the signal is subjected to filtering processing, the signal is still an alternating voltage value after filtering, the size of the signal cannot be directly measured, the signal is converted into direct current voltage through the alternating current-direct current conversion module, and then the data is measured through AD conversion.
If the grounding loop is not a pure resistive load, but the lightning protection performance of the tower is influenced by a resistive part, when the impedance value of the grounding loop is measured or the grounding resistance value of a grounding body is calculated, the resistive part and an inductive part are distinguished, and the phase detection must be carried out on the measured current data, so that a phase detection circuit is arranged. The phase detection circuit performs phase detection on the measured current data, if the current comprises a resistive part and an inductive part, the current detection circuit feeds back the resistive part and the inductive part to the controller together, and the controller calculates the impedance value of the ground loop according to the feedback.
S02), column write node voltage equation:
firstly, an equivalent circuit of a grounding system is constructed, as shown in fig. 2, the grounding system is provided with N downleads, the N downleads are regarded as N parallel branches, the N downleads are grounded through a grounding body, and the equivalent resistance of the N downleads is R1～RNThe equivalent resistance of the grounding body is RgDuring measurement, the measuring voltage applied to the N downleads by the sine voltage generating circuit is U1～UNEach down conductor current is I1～INAnd the voltage at two ends of the grounding body is U, and then according to circuit analysis, the following steps are provided:
I1R1+IRg＝U1，
I2R2+IRg＝U2，
……
InRn+IRg＝Un，
namely, it is
Ui＝IiRi+IRg (1)，
Both ends are divided by IiThe method comprises the following steps:
finishing to obtain:
for N branches, the above equation is added to obtain:
in the formula, the first and second organic solvents are,
the above equation is:
equation (5) is the volt-ampere characteristic equation written in the column;
s03), solving the grounding resistance:
in the grounding system, the equivalent resistance R of the down conductor1～RNThe equivalent resistance value of the grounding body is RgFor the quantity to be solved, N +1 unknown quantities are counted, N +1 groups of measurement voltages are applied to the grounding system by utilizing the sine voltage generating circuit, the current generated by each group of measurement voltages in the grounding system is measured by the current measuring circuit, so that N +1 volt-ampere characteristic equations are obtained, and the equivalent resistance R of each downlead is obtained by solving1～RNEquivalent resistance value of R to grounding bodyg。
In the calculation process, if a certain down conductor fails, the branch is not considered when the column voltage-current characteristic equation is written, and the equation quantity is reduced in sequence.
In this embodiment, the N +1 sets of measurement voltages applied in step S03 are linearly independent, and the N +1 volt-ampere characteristic equations are independent of each other.
The present embodiment takes a grounding system with N down conductors grounded as an example,
the method comprises the following operation steps:
step 1: clamping the 1 st down lead by using a clamp meter method to obtain
Measurement data T1. If T1If the value is larger than the value specified by the grounding resistance measurement operation specification, the fault of the downlead is judged, the downlead is considered to have no influence on the whole grounding system, and the downlead is not considered in the subsequent calculation process. If T1Smaller, then preliminaryIndicating that the downlead state is normal, and retaining the data.
Step 2: for N downlines, the process of the step 1 is repeated to obtain all the measurement data T2～TN. The downleads with normal states and the downleads with faults are classified, and the downleads with normal states can be divided into the 1 st to the k th downlead states and the k +1 th to the N th downlead faults. For the 1 st to k th downleads, the measured data T is reserved1～TkAnd forming k down lead volt-ampere characteristic equations.
The volt-ampere characteristic equation formed in the step 2 only considers one
Values, e.g. first equation only considering
Other values such as
Disregarding; the second equation only takes into account
Other values such as
Disregarding; and by analogy, k downlead volt-ampere characteristic equations are formed.
And step 3: for k downleads in normal state, applying a set of measurement voltages of U'1～U’kRecording measured data I 'of each down conductor current'1～I’kAnd forming a k +1 th downlead volt-ampere characteristic equation.
The volt-ampere characteristic equation formed in the step considers k
Value, hence applying a set of measurement voltages of U'1～U’kOnly one down conductor volt-ampere characteristic equation is formed.
And 4, step 4: and (3) simultaneously forming k +1 equations from the step 1 to the step 3, and measuring an equation set of the grounding system based on the volt-ampere characteristic of the down conductor.
And 5: solving method for equivalent resistance R of down conductor by using solution of nonlinear equation sets such as iteration method and Newton method1～RkThe equivalent resistance value of the grounding body is Rg。
In this embodiment, Ui、IiCan be measured by a current transformer and a voltage transformer and then fed back to a controller, or can be detected by a clamp meteri/IiAnd the detected value is sent to the controller for calculation.
The method can conveniently and comprehensively measure the grounding resistance of the grounding electrode and the resistance of the down lead for the multi-down lead grounding system. Based on a loop method, a voltage transformer is used for inducing voltage to the down conductor, a current transformer is used for collecting the current value on the down conductor, an equation is written in a column mode, the equation is arranged into the voltage-current ratio relation of the down conductor, and the quantity to be solved is obtained. If a certain grounding down lead is disconnected, the system can realize judgment and does not influence the solution of the equation. If a parameter in the circuit is in the form of impedance, the method is still applicable.
The foregoing description is only for the basic principle and the preferred embodiments of the present invention, and modifications and substitutions by those skilled in the art are included in the scope of the present invention.
Claims (4)
1. The ground resistance measurement method based on the volt-ampere characteristic of the down conductor is characterized by comprising the following steps: the method comprises the following steps:
s01), constructing a grounding resistance measuring circuit:
the grounding resistance measuring circuit comprises a controller, a sine voltage generating circuit and a current detecting circuit, wherein the sine voltage generating circuit is used for applying measuring voltage to a plurality of downleads of the grounding system, and the current detecting circuit is used for detecting the current generated by the measuring voltage on the downlead and feeding back the current to the controller;
s02), column current-voltage characteristic equation:
firstly, an equivalent circuit of a grounding system is constructed, the grounding system is provided with N downleads, and the N downleads are viewedN parallel branches, N downleads are grounded through the grounding body, and the equivalent resistance of the N downleads is R1～RNThe equivalent resistance of the grounding body is RgDuring measurement, the measuring voltage applied to the N downleads by the sine voltage generating circuit is U1～UNEach down conductor current is I1～INAnd the voltage at two ends of the grounding body is U, and the grounding body has the following characteristics according to volt-ampere characteristics:
Ui＝IiRi+IRg (1)，
both ends are divided by IiThe method comprises the following steps:
finishing to obtain:
for N branches, the above equations are added to obtain
In the formula (4), the first and second groups,
then equation (4) is:
equation (5) is the volt-ampere characteristic equation written in the column;
s03), solving the grounding resistance:
in the grounding system, the equivalent resistance R of the down conductor1～RNEquivalent resistance value of R to grounding bodygFor the measured quantity, N +1 total unknowns are usedThe sine voltage generating circuit applies N +1 groups of measuring voltages to the grounding system, the current measuring circuit measures the current generated by each group of measuring voltages in the grounding system, so as to obtain N +1 volt-ampere characteristic equations, and the equivalent resistance R of each down lead is obtained by solving1～RNEquivalent resistance value of R to grounding bodyg；
Step S03), the applied N +1 sets of measurement voltages are linearly independent, and the N +1 volt-ampere characteristic equations are independent of each other.
2. The ground resistance measurement method based on the volt-ampere characteristic of the down conductor according to claim 1, wherein: the grounding resistance measuring circuit also comprises a phase detection circuit, the phase detection circuit carries out phase detection on measured current data, if the measured current data comprises a resistive part and an inductive part, the current detection circuit feeds the magnitude and the phase of the current back to the controller, and the controller calculates the impedance value of the grounding loop according to the feedback.
3. The ground resistance measurement method based on the volt-ampere characteristic of the down conductor according to claim 1, wherein: in the calculation process, if a certain down conductor has a fault, the branch is not considered when column voltage-current characteristic equations are written, the number of the equations is reduced in sequence, and the method is still applicable.
4. The ground resistance measurement method based on the volt-ampere characteristic of the down conductor according to claim 1, wherein: detection of U by a clamp meteri/IiAnd the detected value is sent to the controller for calculation.
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